SF_15.1 - https://www.progress.com/documentation/sitefinity-cms/next.js-widget-development

nextjsmapentry.ts

import { WidgetRegistry, initRegistry, defaultWidgetRegistry } from '@progress/sitefinity-nextjs-sdk';
import { HelloWorld } from './components/hello-world/hello-world';
import { HelloWorldEntity } from './components/hello-world/hello-world.entity';

const customWidgetRegistry: WidgetRegistry = {
    widgets: {
        'HelloWorld': {
            componentType: HelloWorld, // registration of the widget
            entity: HelloWorldEntity, // registration of the designer
            editorMetadata: {...} // metadata to be displayed in the WYSIWYG editor - title, available operation, empty content visuals etc.
            ssr: true // whether this is a server rendered or client rendered component
        }
    }
};

customWidgetRegistry.widgets = {
    ...defaultWidgetRegistry.widgets,
    ...customWidgetRegistry.widgets
};

export const widgetRegistry: WidgetRegistry = initRegistry(customWidgetRegistry);